Output of step 6


The output of step 6 is an intermediate language which differs significantly from the user-level language.

General comments

All local variables are recorded in the local symbol table, along with their types.

Except where indicated, all functions take a fixed number of inputs, with a fixed pattern of types, and produce output of a fixed type. Overloading has been resolved by assigning distinct names for different input types. (When compiling into C, later steps may re-introduce overloading for some of these functions.)

The inputs to an arithmetic function are either all integers or all reals. If the original call contained a mixture of real and integer inputs, floating point contagion has been applied to wrap exact->inexact around the integers.

Only structure and sheet accessors and assembly operations take vectors as inputs or produce vector outputs.

Only begin, return, and multiple-set! take a variable number of inputs.

All checking for missing input values has been explicitly coded, as is range checking for point-coordinate.

The head of each expression is marked with its type. The head is a vector, whose first element is the type and whose second element is the operation name.

Control structure

Control primitives: begin, while, return, binary-if, unary-if, set!, multiple-set!, constant-set!, icp-error, and, or, not

While forms do not occur inside expressions.

All return values are enclosed in return forms.

Multiple-set! forms only occur immediately surrounding calls to external co-processor functions which return multiple values.

All calls to other coprocessor functions are directly inside a set! or multiple-set! form.

Type coercion

There are two type coercion functions: inexact->exact (real inputs), exact->inexact (integer inputs)

These operations only need to handle 1D points of the correct type. They need to check whether their input is missing.

Missing values

Handlers for missing values include: missing?, make-missing-real, make-missing-integer

Sheets and samples

Operations on sheets and samples can take points, sheets, or samples of any dimension.

Sheet reference operators: integer-sheet-ref (on-grid reference), real-sheet-ref (interpolated reference), unscaled-sheet-set!

Scaling and offset: sheet-domain-scaling, sheet-domain-offset, sheet-codomain-scaling, sheet-codomain-offset

Samples: sheet-min-sample, sheet-max-sample, focus-min-sample, focus-max-sample, sample-unscaled-point, sample->sheet, make-sample


Vector structure accessors: make-point, point-coordinate

Numerical tests

Integer-only numerical tests: =

Real or integer numerical tests: <, >, <=, >=

Real arithmetic operations

These functions always take real inputs and return a single real output. They do not take vector inputs.

unary: log, exp, sqrt, sin, cos, tan, asin, acos, unary-atan, floor, ceiling, round, truncate

binary: random-real, binary-atan, expt, /, guaranteed-/

The coprocessor code for these operations must check the following conditions and return a missing value in these cases:

Guaranteed-/ is a form of / whose second input cannot be zero, created during expansion of sheet-ref and sample-set!.

Integer arithmetic operations

These functions always take integer inputs and return a single integer output.

unary: bitwise-not

binary: bitwise-and, bitwise-ior, bitwise-xor, arithmetic-shift, remainder, quotient, modulo, guaranteed-quotient guaranteed-modulo

An error should be flagged if the second input to remainder, quotient, or modulo is zero. Guaranteed-quotient and guaranteed-modulo are versions of quotient and modulo whose second inputs cannot be zero. They are created during expansion of sheet-ref and sample-set!.

Real/integer arithmetic operations

These functions have two variants: one handles integer inputs and the other handles real inputs.

unary: unary-minus, abs

binary: min, max, +, -, *


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