Functional Programming Research Articles

Translation, extension, and evaluation of usability, usefulness, and safety of a fall prevention and management program for people living with spinal cord injury and multiple sclerosis who use wheelchairs or scooters full time.

Falls are prevalent among people living with Multiple Sclerosis (PwMS) and Spinal Cord Injury (PwSCI) who use wheelchairs or scooters (WC/S) full time, however, there is a scarcity of evidence-based fall prevention and management programs. To describe the systematic translation of an in-person fall prevention and management program (Individualized Reduction Of FaLLs - iROLL) for PwMS to an online platform, extending its scope to include PwSCI, and to evaluate the preliminary useability, usefulness, and safety of the intervention. iROLL was systematically translated to an online platform (iROLL-O). PwMS and PwSCI who use a WC/S full time, experienced at least one fall within the past 36 months, and could transfer independently or with minimal to moderate assistance, enrolled in iROLL-O. Usability, usefulness, and safety were evaluated through 1:1 semi-structured interviews, gathering feedback on: perceived impact of the intervention on falls and functional mobility, program experiences, adverse events, and recommendations for improvement. Five participants successfully completed the iROLL-O program. No safety concerns were raised by participants. Themes emerging from the semi-structured interviews included: (1) barriers and facilitators to program access, (2) motivation for participation, (3) program outcomes, and (4) program content and structure. Participants reported reduced concerns about falling, enhanced functional mobility skills, and highlighted the supportive nature of synchronous group meetings for learning. No adverse events occurred during the implementation of iROLL-O and participants found the program to be useable and useful. Further testing is needed to examine efficacy among a large and diverse population.

Influence of Mentorship Programs on Students’ Academic Performance in Public Secondary Schools in Imenti North Sub- County, Meru County, Kenya

Management practices are an important ingredient in an organization. They offer a unique environment needed to attain set goals, create a good public image and build a productive relationship among the stakeholders. The main aim of this study was to determine the influence of teacher satisfaction on the academic performance of learners in public secondary schools in Imenti North sub-county, Meru County. The study was based on organizational theory, which was developed by Jaques in 1951. The study adopted a mixed methods methodology where both quantitative and qualitative methods were employed. The sampling unit consisted of public secondary schools where 6 principals were selected through purposive sampling from the top three and bottom three performing schools. Ten form three and form four students were also randomly selected from the top three and bottom three performing schools to obtain a sample size of 120 students. Data was collected using a structured questionnaire. Data collected was analyzed using descriptive and inferential statistics with the help of the statistical package for social scientists, version 26.0. A multiple Linear Regression model was used to model the relationship between the independent variable and the response variable (academic performance). The study concludes that mentorship programs have a significant positive effect on academic performance, as indicated by their p-values (P<0.05). The study recommends that schools should ensure that there are functional mentoring programs in schools, as they have been shown to positively influence academic performance. Such programs may provide guidance, support and career direction.

Interdisciplinary pain program participants with high catastrophizing scores improve function utilizing enriched therapeutic encounters and integrative health techniques: a retrospective study.

Pain catastrophizing describes helplessness, rumination, and magnification of a pain experience. High pain catastrophizing is an independent risk factor for disability, pain severity, inadequate treatment response, chronicity, and opioid misuse. Interdisciplinary pain programs (IPPs) are beneficial and cost-effective for individuals with chronic pain, but their functional impact on individuals with high pain catastrophizing is not well established. The emerging field of placebo studies suggests that patient-provider relationships, positive treatment expectations, and sociobiologically informed care trigger physiological responses that may enhance therapeutic interventions. In this retrospective observational cohort study, we compared admission and discharge data for 428 adults with high-impact chronic pain (mean 8.5 years) who completed the Spaulding-Medford Functional Restoration Program (FRP). The interdisciplinary FRP team of physiatrists, behavioral health clinicians, physical therapists, and occupational therapists specializes in evidenced-based conventional rehabilitation, integrative health, and pain psychoeducation via enriched therapeutic encounters, fostering collaboration, validation, trust, self-efficacy, and positive expectations. Clinical outcome measures included the Canadian Occupational Performance Measure (COPM) assessing functional performance (COPM-PS) and satisfaction with function (COPM-SS), the Pain Numeric Rating Scale (NRS), the Pain Catastrophizing Scale (PCS), and the Patient Health Questionnaire-9 (PHQ-9). FRP participants with clinically elevated catastrophizing at baseline (PCS ≥30, mean PCS 39) achieved statistically significant improvements in function (mean delta -2.09, CHI2 = 15.56, p < 0.001), satisfaction with function (COPM-SS mean delta -2.50, CHI2 = 7.42, p = 0.007), pain (NRS mean delta 2.7), mood (PHQ-9 mean delta 1.87, p = 0.002), and catastrophizing (PCS mean delta 4.16, p < 0.001). Subgroup analysis revealed racial disparities in pain scores, and exploratory analysis showed a trend toward reducing opiate consumption. Despite the known association of adverse outcomes with high catastrophizing, FRP participation was associated with increased productive engagement, reduced pain, reduced maladaptive thought processes, and improved mood. Although causation and efficacy cannot be established from a retrospective design, this is the first study to identify functional improvement in patients with high-impact chronic pain and clinically relevant high pain catastrophizing who participate in an IPP combining conventional and complementary rehabilitation with psychoeducation. These enriched therapeutic encounters may enhance the treatment process by promoting trust, empathy, collaboration, and beneficial reframing of patients' experiences, expectations, and goals.

A - 147 Patient-Centric Considerations for Selecting the Language of Procedure Administration in Candidates for Epilepsy Surgery: Implications for Data Interpretation, Prognostication and Outcomes

Abstract Objective Selecting the language of pre-surgical neuropsychological testing (NPT), intracarotid amobarbital procedure, and intra/extra functional language mapping (ESM) in bi−/multi-lingual patients is a high-stakes neuropsychological decision point. Though a patient’s self-selection of language is an integral consideration, both patient and provider must fully understand the potential implications of language selection on a patient’s data interpretation and overall case conceptualization. Method A 26-year-old, right-handed, bilingual (L1 = Mandarin-, L2 = English-speaking) female received pre-operative NPT, Wada test, and ESM to guide resective surgery targeting medically-refractory epilepsy involving the right superior temporal gyrus (STG) and mesial (MTL) temporal lobe. All procedures were conducted in English at the patient’s request with alternate forms of verbally-mediated NPT administered in Mandarin. Results Confrontation naming and verbal fluencies were impaired in both English and Mandarin. Wada testing administered in English revealed bilateral language and greater left hemisphere memory support. Following considerable psychoeducation regarding possible functional language loss in Mandarin post-operatively, the patient agreed to ESM in L1 with auditory and picture naming disruption after right STG stimulation. Conclusion Despite strong English-language fluency, assessment in Mandarin was of critical importance, as eloquent cortices essential for tonal language production may have been resected if mapping procedures were completed in English-only, as requested. Balancing factors informed by functional and structural neuroanatomy, patient worldview, and cross-cultural neuropsychology requires a tailored, patient-centric approach to case conceptualization.

Molecular programs guiding arealization of descending cortical pathways.

Layer 5 extratelencephalic (ET) neurons are present across neocortical areas and send axons to multiple subcortical targets1-6. Two cardinal subtypes exist7,8: (1) Slco2a1-expressing neurons (ETdist), which predominate in the motor cortex and project distally to the pons, medulla and spinal cord; and (2) Nprs1- or Hpgd-expressing neurons (ETprox), which predominate in the visual cortex and project more proximally to the pons and thalamus. An understanding of how area-specific ETdist and ETprox emerge during development is important because they are critical for fine motor skills and are susceptible to spinal cord injury and amyotrophic lateral sclerosis9-12. Here, using cross-areal mapping of axonal projections in the mouse neocortex, we identify the subtype-specific developmental dynamics of ET neurons. Whereas subsets of ETprox emerge by pruning of ETdist axons, others emerge de novo. We outline corresponding subtype-specific developmental transcriptional programs using single-nucleus sequencing. Leveraging these findings, we use postnatal in vivo knockdown of subtype-specific transcription factors to reprogram ET neuron connectivity towards more proximal targets. Together, these results show the functional transcriptional programs driving ET neuron diversity and uncover cell subtype-specific gene regulatory networks that can be manipulated to direct target specificity in motor corticofugal pathways.

Improved socio-emotional skills in students with autism spectrum disorder (ASD) following an intervention supported by an augmented gamified environment

This study examines the impact of an intervention using an Augmented Gamified Environment (AGE) to stimulate socio-emotional skills in a sample of 54 subjects with Autism Spectrum Disorder (ASD) aged between 3 and 17 years old. The study used a quantitative, exploratory, analytical methodology. Socio-emotional skills were evaluated before and after intervention (pre-posttest) using the DiagnosticApp instrument, supported by a fun app. The study specifically analyzed their ability to identify primary and secondary emotions and emotional states, as well as the cause-effect relationship linked to a context. The results show that socio-emotional skills improved after the intervention, regardless of gender, age, degree of ASD, comorbidity, or type of language. Overall, the greatest improvement was in identifying both primary and secondary emotions through recognizing facial expressions. Additionally, as expected, older students, and those with less severe ASD and more functional language exhibited higher scores in their socio-emotional skills. In conclusion, the extrinsic motivation associated with the mix of game mechanics, dynamics, and aesthetics, along with the augmented reality resources making up the AGE, are key contributing elements in improving these students’ socio-emotional skills.

Age-dependencies of the electroretinogram in healthy subjects.

The purpose of this study was to evaluate the age-dependency of amplitudes and implicit times in the electroretinograms (ERGs) of healthy individuals and provide clinicians and researchers with a reference for a variety of stimulus paradigms. Full-field electroretinography was conducted on 73 healthy participants aged 14-73 using an extended ISCEV standard protocol that included an additional 9Hz flicker stimulus for assessing rod function and special paradigms for isolated On-Off and S-cone responses. Correlation coefficients and best-fit regression models for each parameter's age-dependency were calculated. Dark-adapted ERGs, in particular, displayed notable age-related alterations. The attenuation and delay of the b-wave with higher age were most significant in the dark-adapted, rod-driven 0.001cds/m2 flash ERG. The age-dependent reduction of the a-wave amplitude was strongest in the standard dark-adapted 3cds/m2 flash condition. Cone-driven, light-adapted responses to either flash or flicker stimuli displayed comparatively small alterations at higher age. S-cone function tended to diminish at an early age, but the effect was not significant in the whole population. The results suggest that rod and cone function decline at different rates with age, with rods being generally more affected by aging. Nonetheless, response amplitudes displayed a wide variability across the whole sample.

Imperative Genetic Programming

Genetic programming (GP) has a long-standing tradition in the evolution of computer programs, predominantly utilizing tree and linear paradigms, each with distinct advantages and limitations. Despite the rapid growth of the GP field, there have been disproportionately few attempts to evolve ’real’ Turing-like imperative programs (as contrasted with functional programming) from the ground up. Existing research focuses mainly on specific special cases where the structure of the solution is partly known. This paper explores the potential of integrating tree and linear GP paradigms to develop an encoding scheme that universally supports genetic operators without constraints and consistently generates syntactically correct Python programs from scratch. By blending the symmetrical structure of tree-based representations with the inherent asymmetry of linear sequences, we created a versatile environment for program evolution. Our approach was rigorously tested on 35 problems characterized by varying Halstead complexity metrics, to delineate the approach’s boundaries. While expected brute-force program solutions were observed, our method yielded more sophisticated strategies, such as optimizing a program by restricting the division trials to the values up to the square root of the number when counting its proper divisors. Despite the recent groundbreaking advancements in large language models, we assert that the GP field warrants continued research. GP embodies a fundamentally different computational paradigm, crucial for advancing our understanding of natural evolutionary processes.

Analysis of Unfolded Protein Response Activation in Colon Adenocarcinoma Epithelial Cells: A Proteomic Study.

High throughput technologies have identified molecular patterns in colorectal cancer (CRC) cells, aiding in modeling responses to anti-cancer treatments. The different responses observed depend on the type of cancer, the tumour grade and the functional programme of the cancer cells. Recent studies suggest that the unfolded protein response (UPR), autophagy and apoptosis could be involved in treatment resistance mechanisms by interacting with the tumour microenvironment (TME). We analysed by LC-MS/MS the proteome of two representative colon adenocarcinoma epithelial cell lines from different tumour grades (CCL-233 and CCL-221) at the basal state or after the UPR induction. Cell lines expressed a different proteome on about 10% of their total proteins identified, especially on UPR, autophagy and apoptosis pathways proteins at basal state. After UPR induction, the proteome of the cells was modified with a greater adaptive response to cellular stress in CCL-221 cells where the UPR was strongly activated at the basal state. CRC cell lines at different tumour grades expressed different functional programmes at the proteomic level and were characterised by different responses to the UPR induction. This study suggests that baseline cancer cell stress status could have an impact on the efficiency of cancer therapies.

Impact of short-term functional training program on lower-body isometric muscle endurance in cricket players

Impact of short-term functional training program on lower-body isometric muscle endurance in cricket players

Enhancing Physical Fitness in Elite Field Hockey Players with A Twelve-Week Functional Training Program: A Cluster Randomized Control Trial.

This study aimed to explore the impact of functional training on the physical fitness of young elite field hockey players. The study comprised 40 young elite male field hockey players with the following characteristics (mean ± SD age: 21.5 ± 0.8 years; height: 176.9 ± 2.6 cm; weight: 68.4 ± 5.1 kg; BMI: 21.8 ± 1.3; training experience: 51.2 ± 5.4 months). Twenty participants were allocated to two groups: the functional training group (FTG) and the control training group (CG). Each group received 60-minute training sessions three times per week for 12 weeks. Generalized estimating equation analysis and a Bonferroni test for pairwise comparisons were used to assess the intervention's efficacy. Before the start of the exercise program, no statistically significant differences were observed in physical fitness measures between the FTG and CG (p > 0.05). However, by the sixth week, a significant difference appeared in both the T-Agility test (p < 0.001) and endurance (p = 0.024) between the two groups, while no notable distinctions were detected in other fitness parameters (p > 0.05). After a 12-week training program, the FTG demonstrated improvements in all physical fitness measures [flexibility (p < 0.001); Illinois agility test (p < 0.001); T-agility test (p = 0.020); endurance (p < 0.001)] except speed, which exhibited no significant impact (p = 0.175). Notable enhancements in T-agility and endurance were evident after just six weeks of functional training, and a 12-week functional training regimen showed superiority over standard training approaches in young elite male field hockey players. These findings encourage the efficacy of functional training exercises over traditional methods in enhancing athletes' fitness parameters.

Exploring the Utility of a Functional Magnetic Resonance Imaging Cannabis Cue-Reactivity Paradigm in Treatment-Seeking Adults With Cannabis Use Disorder

BackgroundFunctional magnetic resonance imaging studies examining cue reactivity in cannabis use disorder (CUD) either have had small sample sizes or have involved non–treatment-seeking participants. As a secondary analysis, we administered a functional magnetic resonance imaging cue-reactivity task to participants with CUD enrolled in 2 separate clinical trials (varenicline or repetitive transcranial magnetic stimulation) to determine the task activation patterns for treatment-seeking participants with CUD. We aimed to determine the activation patterns for the total sample and behavioral correlates. We additionally compared studies to determine if patterns were consistent. MethodsTreatment-seeking participants with moderate or severe CUD had behavioral craving measured at baseline using the Marijuana Craving Questionnaire–Short Form and completed a visual cannabis cue-reactivity task during functional magnetic resonance imaging (measuring the blood oxygen level–dependent response) following 24 hours of cannabis abstinence. ResultsThe sample included 65 participants (n = 37: varenicline trial; n = 28: repetitive transcranial magnetic stimulation trial; 32% female; mean age = 30.4 ± 9.9 years). When comparing cannabis images versus matched neutral images, participants showed greater blood oxygen level–dependent response in bilateral ventromedial-prefrontal, dorsolateral-prefrontal, anterior cingulate, and visual cortices as well as the striatum. There was stronger task-based functional connectivity between the medial prefrontal cortex and both the amygdala and the visual cortex. Craving negatively correlated with blood oxygen level–dependent response in the left ventral striatum (R2 = −0.32; p = .01) in the full sample. There were no significant differences in either activation or task-based functional connectivity between studies. ConclusionsIn 2 separate treatment-seeking groups with CUD, there was increased cannabis cue reactivity and task-based functional connectivity in regions related to executive function and reward processing. Cannabis craving was negatively associated with cue reactivity in the left ventral striatum.

Language networks of normal-hearing infants exhibit topological differences between resting and steady states: An fNIRS functional connectivity study.

Task-related studies have consistently reported that listening to speech sounds activate the temporal and prefrontal regions of the brain. However, it is not well understood how functional organization of auditory and language networks differ when processing speech sounds from its resting state form. The knowledge of language network organization in typically developing infants could serve as an important biomarker to understand network-level disruptions expected in infants with hearing impairment. We hypothesized that topological differences of language networks can be characterized using functional connectivity measures in two experimental conditions (1) complete silence (resting) and (2) in response to repetitive continuous speech sounds (steady). Thirty normal-hearing infants (14 males and 16 females, age: 7.8 ± 4.8 months) were recruited in this study. Brain activity was recorded from bilateral temporal and prefrontal regions associated with speech and language processing for two experimental conditions: resting and steady states. Topological differences of functional language networks were characterized using graph theoretical analysis. The normalized global efficiency and clustering coefficient were used as measures of functional integration and segregation, respectively. We found that overall, language networks of infants demonstrate the economic small-world organization in both resting and steady states. Moreover, language networks exhibited significantly higher functional integration and significantly lower functional segregation in resting state compared to steady state. A secondary analysis that investigated developmental effects of infants aged 6-months or below and above 6-months revealed that such topological differences in functional integration and segregation across resting and steady states can be reliably detected after the first 6-months of life. The higher functional integration observed in resting state suggests that language networks of infants facilitate more efficient parallel information processing across distributed language regions in the absence of speech stimuli. Moreover, higher functional segregation in steady state indicates that the speech information processing occurs within densely interconnected specialized regions in the language network.

Impact of Hospital Dentistry on Patients' Food Intake Status in Convalescent Rehabilitation Ward.

Treating oral problems with dentist intervention during hospitalisation may improve patients' food intake status. This study aimed to clarify whether convalescent rehabilitation ward inpatients in a hospital with hospital dentistry (HHD) had a better diet at discharge than those in a hospital without hospital dentistry (HNHD). Retrospective observational study including inpatients with dental involvement in a HHD with dentists and dental hygienists and HNHD with dental hygienist and visiting dental service between 1 March and 31 August 2022. Data included age, sex, body mass index (BMI), Functional Independent Measure (FIM) motor and cognitive, Oral Health Assessment Tool (OHAT) score, Food Intake LEVEL Scale (FILS), whether the FILS ≥8 (indicating that patient eats also a non-texture-modified diet), remained and functional tooth numbers and speech language hearing therapist (SLHT) and dentist interventions. Comparisons between the two hospitals and factors that affected the FILS ≥8 were examined. A total of 333 and 89 inpatients were included in the HHD and HNHD groups, respectively. After propensity score matching, the HHD group had a significantly higher rate of FILS ≥8, functional tooth numbers at discharge, and SLHT and dentist intervention rates. The multivariable logistic regression analysis for propensity score matching participants showed that the significant independent variables for FILS ≥8 were age, BMI, FILS, FIM motor (all at admission) and SLHT and dentist interventions. Odds ratio for dentist intervention was 14.46 (95% CI: 4.36-48.01). Dentists are necessary to improve patients' food intake status in convalescent rehabilitation wards.

Functional Programming for the Internet of Things: A Comparative Study of Implementation of a LoRa-MQTT Gateway Written in Elixir and C++

Functional Programming for the Internet of Things: A Comparative Study of Implementation of a LoRa-MQTT Gateway Written in Elixir and C++

Research on Constant-Flow Water-Saving Device Based on Dynamic Mesh Transient Flow Field Analysis

For the control of the outlet flow rate of a constant-flow water-saving device under different water pressures, this study developed and implemented a custom User-Defined Function (UDF) program to simulate the dynamic motion of the water-saving valve within the Fluent environment. This simulation realistically represents the valve’s behavior under varying water pressures, thereby accurately predicting the valve opening height to comply with national regulatory standards. Firstly, a dynamic grid transient CFD simulation model of the water-saving valve was established using a Fluent UDF program written in C language. The parameters of the elastic elements in the water-saving device flow control system were designed to achieve control of the outlet flow rate. Then, the benchmarking analysis of the aforementioned simulation model was completed based on the flow rate test results of the water-saving device. Finally, the relationship between physical quantities and flow field distribution characteristics of the water-saving valve was analyzed under three different water pressures specified in the national standard. Based on the optimization calculations, the valve opening heights under three different water pressures were obtained, ensuring that the outlet flow rates meet the regulatory standards set by the national authorities. Compared with traditional methods that rely solely on steady-state simulations or empirical data, the method proposed in this paper represents a significant advancement.

A Functional Restoration Program for Active Duty Service Members With Chronic Pain: Examining the Impact of Co-occurring PTSD on Treatment Response.

Standard medical intervention for chronic pain may be less effective in the presence of co-occurring PTSD. Functional restoration programs (FRPs), which combine psychological interventions and progressive exercise rehabilitation, represent an alternative to standard medical intervention for chronic pain. The objective of the current study is to evaluate a FRP serving Active Duty Service Members with chronic pain and to examine whether co-occurring PTSD symptoms are associated with differential treatment response. This is a retrospective observational study of data previously collected at Naval Medical Center San Diego approved by the Naval Medical Center San Diego Institutional Review Board. The study included 81 Active Duty Service Members, primarily Sailors and Marines, who completed a FRP, and examined pre- to post-treatment changes in Pain Impact Score-a composite measure of pain intensity, pain interference, and physical functioning-as well as measures of mental health and pain cognitions. Co-occurring PTSD symptoms were examined as a potential moderator of treatment response. Twenty-three patients (28.4%) screened positive for PTSD during baseline assessments. Repeated measures analysis of variance showed statistically significant improvement in Pain Impact Score for the full sample (P <.001). Although no significant interactions with probable PTSD were demonstrated for measures of pain intensity and physical functioning (both Ps >.05), patients screening positive for PTSD demonstrated a lesser decrease in pain interference compared to patients screening negative for PTSD (P <.01). Improvements in measures of mental health and pain cognitions were also statistically significant for the full sample (all P values <.05) and did not differ as a function of PTSD symptoms (all P values >.05). This FRP primarily serving Sailors and Marines contributed to broad overall improvements in the domains of pain and functioning as well as mental health and pain cognitions. Co-occurring PTSD symptoms were not associated with poorer treatment response on most measured outcomes.

Functional Programming in Financial Markets (Experience Report)

We present a case-study of using functional programming in the real world at a very large scale. At Standard Chartered Bank, Haskell is used in a core software library supporting the entire Markets division -- a business line with 3 billion USD operating income in 2023. Typed functional programming is used across the entire tech stack, including foundational APIs and CLIs for deal valuation and risk analysis, server-side components for long-running batches or sub-second RESTful services, and end-user GUIs. Thousands of users across Markets interact with software built using functional programming, and over one hundred write functional code. In this experience report we focus on how we leverage functional programming to orchestrate type-driven large-scale pricing workflows. The same API can be used to price one trade locally, or millions of trades across thousands of cloud nodes. Different parts of the computation can be run and inspected individually, and recomputing one part triggers recalculation of the dependent parts only. We build upon decades of research and experience in the functional programming community, relying on concepts such as monads, lenses, datatype generics, and closure serialisation. We conclude that the use of functional programming is one of the main drivers of the success of our project, and we see no significant downsides from it.

The Functional, the Imperative, and the Sudoku: Getting Good, Bad, and Ugly to Get Along (Functional Pearl)

Conventional wisdom suggests that the benefits of functional programming no longer apply in the presence of even a small amount of imperative code, as if the addition of imperative code effectively subtracts. And yet, as we show in this paper, combining functional programming with the special imperative language Esterel provides a multiplicative improvement to the benefits of functional programming. The key to the benefit of both Esterel and functional programming stems from a restriction that both share. As in functional programming, where only the inputs to a function determine its outputs, the state of an Esterel computation is fully determined by the program’s input and the state that the computation had in the previous time step, where the notion of a time step is explicit in the language. Esterel’s guarantee holds even though Esterel programs feature concurrent threads, mutable state, and the ability to create, suspend, and even terminate threads as the computation proceeds. This similarity is the root of the benefits that programmers accrue as they informally reason about their program’s behavior. To illustrate these benefits, the bulk of this paper consists of an in-depth exploration of HipHop code (a mashup of JavaScript and Esterel) that implements a Sudoku solver, showing how it is possible to write code that is as easy to understand as if it were written in a pure functional programming style, even though it uses multiple threads, mutable state, thread preemption, and even thread abortion. Even better, concurrent composition and task canceling provide significant program structuring benefits that allow a clean decomposition and task separation in the solver.

Double-Ended Bit-Stealing for Algebraic Data Types

Algebraic data types are central to the development and evaluation of most functional programs. It is therefore important for compilers to choose compact and efficient representations of such types, in particular to achieve good memory footprints for applications. Algebraic data types are most often represented using blocks of memory where the first word is used as a so-called tag, carrying information about the constructor, and the following words are used for carrying the constructor's arguments. As an optimisation, lists are usually represented more compactly, using a technique called bit-stealing, which, in its simplest form, uses the word-alignment property of pointers to byte-addressed allocated memory to discriminate between the nil constructor (often represented as 0x1) and the cons constructor (aligned pointer to allocated pair). Because the representation supports that all values can be held uniformly in one machine word, possibly pointing to blocks of memory, type erasure is upheld. However, on today's 64-bit architectures, memory addresses (pointers) are represented using only a subset of the 64 bits available in a machine word, which leave many bits unused. In this paper, we explore the use, not only of the least-significant bits of pointers, but also of the most-significant bits, for representing algebraic data types in a full ML compiler. It turns out that, with such a particular utilisation of otherwise unused bits, which we call double-ended bit-stealing, it is possible to choose unboxed representations for a large set of data types, while still not violating the principle of uniform data-representations. Examples include Patricia trees, union-find data structures, stream data types, internal language representations for types and expressions, and mutually recursive ASTs for full language definitions. The double-ended bit-stealing technique is implemented in the MLKit compiler and speedup ranges from 0 to 26 percent on benchmarks that are influenced by the technique. For MLKit, which uses abstract data types extensively, compilation speedups of around 9 percent are achieved for compiling MLton (another Standard ML compiler) and for compiling MLKit itself.