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'''at''' is a primitive that unifies list indexing, function application, and dictionary lookup into a single concept. Syntactically, it can be expressed in three equivalent ways: <code>x@y</code> (using <code>@</code> as a verb), <code>x y</code> (juxtaposition of nouns), and <code>x[y]</code> (M-expression). |
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"abc"[1] |
"abc"[1] |
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"b" |
"b" |
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Revision as of 21:29, 8 July 2022
At
x@y
at is a primitive that unifies list indexing, function application, and dictionary lookup into a single concept. Syntactically, it can be expressed in three equivalent ways: x@y (using @ as a verb), x y (juxtaposition of nouns), and x[y] (M-expression).
"abc"[1]
"b"
{1+2*x}@3
7
(`a`b!0 1)`b
1
If y is an atom not in the domain of x, at returns the null value for x's type (except in kona).