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Instant-use add-on functions for the Wolfram Language
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Replace parts of an expression using replacement rules and a part specification
ResourceFunction["ReplaceAt"][expr,rules,n] transforms expr by replacing the nth element using rules. | |
ResourceFunction["ReplaceAt"][expr,rules,{i,j,…}] replaces the part of expr at position {i,j,…}. | |
ResourceFunction["ReplaceAt"][expr,rules,{{i1,j1,…},{i2,j2,…},…}] replaces parts at several positions. | |
ResourceFunction["ReplaceAt"][rules,pos] represents an operator form of ResourceFunction["ReplaceAt"] that can be applied to an expression. |
Replace a specified part of an expression using a rule:
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Replace multiple parts:
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Replace a nested part:
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Use negative positions to count from the end:
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Use pattern-based replacements:
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Use multiple replacement rules:
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Replace the second element of all top-level parts (the “second column”):
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Replace parts of an association specified by Key:
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Use the operator form of ReplaceAt:
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A single element of the expression:
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Negative numbers count from the end:
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Replace parts at level 2:
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Replace several parts:
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Replace several nested parts:
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Use Span syntax:
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ReplaceAt can be used on expressions with any head:
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Key and integer part specifications in associations are different:
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Use part 0 to perform replacements in the head of an expression:
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ReplaceAt can be used with sparse arrays:
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ReplaceAt can use lists of parts returned by Position:
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These are the subexpressions returned by Extract:
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ReplaceAt can use an Association for replacement rules:
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ReplaceAt can use a Dispatch object for replacement rules:
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ReplaceAt applies replacement rules repeatedly if a part is mentioned repeatedly:
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ReplaceAt will not evaluate held replacements:
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Manipulate code in an unevaluated association:
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Evaluate upon retrieval:
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Use Unevaluated to perform replacements prior to evaluating expr:
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Repeated replacement parts may produce unexpected results if the structure of the expression is expected to change during replacements:
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Compare to using Nest:
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This behavior is consistent with ReplacePart and MapAt:
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Modify the resource functions in a piece of code before running it:
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This work is licensed under a Creative Commons Attribution 4.0 International License