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| Date: Thu, 30 Dec 2004 20:53:37 -0800 | From: Per Bothner <per@xxxxxxxxxxx> | | bear wrote: | | > My own preference would be something like [3 instead of #A3( | | Let's not invent new confusing syntax when we have existing | confusing syntax that is just as good ... | | Array syntax should be compatible with Common Lisp's notation. | Anything else requires a *really* strong justification. | | If you want to *extend* the Common Lisp syntax with a type | specifier, that is ok. But that should be done with type | specifiers. So don't use crypic abbreviations; use type | names that can form the basis for optional type specifiers. | (See below for more on this.) | | Suggestion 1: | | A two-by-two array of unsigned 16-bit integers: | | #2a:int16((0 1) (2 3)) Using a delimiter inside the #-tag is an excellent idea! How detailed should the type specifier be? Is int16 signed or unsigned? | Suggestion 2: | | Many Scheme use <TYPENAME> by convention for class- an/or type-names. | We could incorporate this syntax: | | #2a<int16>((0 1) (2 3)) | | I agree with the goals of srfi-58. Unfortunately, it builds | on srfi-47, which I don't care for. I'd prefer: | (make-array <element-type-specifier> elements ..) | where an <element-type-specifier> might be something | like <int16>. Early versions of MAKE-UNIFORM-ARRAY took a type-specifying argument as you suggest. There were several problems: (Functional) APL operators must construct new arrays of the proper type, usually the same type as an argument array. This required a procedure to extract the type from an array. In an implementation that did not support the full panoply of SRFI-47 types, this ARRAY-TYPE procedure exposed the underlying uniform-type support. Code which used ARRAY-TYPE conditioned its range-checking and coercion on the type of the storage, rather than the type the coder intended. This led to platform-dependencies in the execution of code using arrays. A separate intended-type could have been stored with the array. But this meant the Scheme vectors could no longer simply be the default rank-1 arrays; they would have required wrappers. The arrangement in SRFI-47 portably solved both the type specification and initial value problems (how to specify uninitialized array contents to MAKE-ARRAY) in a single argument. I find SRFI-47 uniform arrays work well in Scheme applications like image processing and computer graphics, sequence comparison, and EM field calculations (optics) and spectra (color).