ref: 61870c24fae357b78029ce54be0c004e1ffdb3c7
parent: 611dced75f0a6c9fd4b35b88ee0dd9ac5806cb54
author: henesy <devnull@localhost>
date: Mon Dec 7 20:11:57 EST 2020
add arrays.m
--- /dev/null
+++ b/appl/lib/arrays.b
@@ -1,0 +1,114 @@
+implement Arrays;
+
+include "arrays.m";
+
+# Return the array 'a' for which 'f' is fulfilled on its contents
+filter[T](a: array of T, f: ref fn(x: T): int): array of T {+ if(a == nil)
+ return nil;
+
+ if(f(a[0]))
+ return prepend(filter(tail(a), f), a[0]);
+
+ if(len a < 2)
+ return nil;
+
+ return filter(tail(a), f);
+}
+
+# Return the array 'a₀' with the function 'f' applied to its contents
+map[T](a₀: array of T, f: ref fn(x: T): T): array of T {+ if(a₀ == nil)
+ return nil;
+
+ a₁ := array[len a₀] of T;
+
+ for(i := 0; i < len a₀; i++)
+ a₁[i] = f(a₀[i]);
+
+ return a₁;
+}
+
+# Create an array whose contents are the pairs of two equally-sized arrays
+pair[T₁, T₂](a₁: array of T₁, a₂: array of T₂): array of (T₁, T₂) {+ if(a₁ == nil || a₂ == nil || len a₁ != len a₂)
+ return nil;
+
+ a₃ := array[len a₁] of (T₁, T₂);
+
+ for(i := 0; i < len a₁; i++)
+ a₃[i] = (a₁[i], a₂[i]);
+
+ return a₃;
+}
+
+# Find instance of 'x' in 'l', return tail of 'l' from and including 'x'
+find[T](a: array of T, x: T): array of T
+ for {+ T => Equals: fn(a, b: T): int;
+ }
+{+ for(i := 0; i < len a; i++)
+ if(T.Equals(x, a[i]))
+ return tail(a[i:]);
+
+ return nil;
+}
+
+# Return the array 'a₀' with 'x' prepended
+prepend[T](a₀: array of T, x: T): array of T {+ if(a₀ == nil)
+ return array[1] of { * => x };+
+ a₁ := array[len a₀ + 1] of T;
+ a₁[0] = x;
+
+ for(i := 1; i < len a₁; i++)
+ a₁[i] = a₀[i-1];
+
+ return a₁;
+}
+
+# Return the array 'a₀' with 'x' appended
+append[T](a₀: array of T, x: T): array of T {+ if(a₀ == nil)
+ return array[1] of { * => x };+
+ a₁ := array[len a₀ + 1] of T;
+ a₁[len a₁ - 1] = x;
+
+ for(i := 0; i < len a₁ -1; i++)
+ a₁[i] = a₀[i];
+
+ return a₁;
+}
+
+# Return 'a[1:]' if possible, or nil
+tail[T](a: array of T): array of T {+ if(a == nil || len a < 2)
+ return nil;
+
+ return a[1:];
+}
+
+# Return a pretty string representing the array
+stringify[T](a: array of T): string
+ for {+ T => String: fn(a: self T): string;
+ }
+{+ if(a == nil) {+ return "[]\n";
+ }
+
+ s := "[";
+
+ for(i := 0; i < len a; i++) {+ s += a[i].String();
+
+ if(i < len a - 1)
+ s += ", ";
+ }
+
+ return s + "]\n";
+}
--- /dev/null
+++ b/module/arrays.m
@@ -1,0 +1,24 @@
+Arrays: module
+{+ PATH: con "/dis/lib/arrays.dis";
+
+ filter: fn[T](a: array of T, f: ref fn(x: T): int): array of T;
+
+ map: fn[T](a₀: array of T, f: ref fn(x: T): T): array of T;
+
+ pair: fn[T₁, T₂](a₁: array of T₁, a₂: array of T₂): array of (T₁, T₂);
+
+ find: fn[T](a: array of T, x: T): array of T
+ for { T => Equals: fn(a, b: T): int; };+
+ prepend: fn[T](a₀: array of T, x: T): array of T;
+
+ append: fn[T](a₀: array of T, x: T): array of T;
+
+ tail: fn[T](a: array of T): array of T;
+
+ # Return a pretty string representing the array
+ stringify: fn[T](a: array of T): string
+ for { T => String: fn(a: self T): string; };+
+};