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Using a function in env= fails #6026

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MichaelChirico opened this issue Mar 28, 2024 · 2 comments · May be fixed by #6027
Open

Using a function in env= fails #6026

MichaelChirico opened this issue Mar 28, 2024 · 2 comments · May be fixed by #6027
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@jangorecki
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bug programming parameterizing queries: get, mget, eval, env

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@MichaelChirico
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DT=data.table(a=1:2, b=3:4)
DT[, f(b), by=a, env=list(f=sum)]
# Error in as.character(jsub[[1L]]) : 
#   cannot coerce type 'builtin' to vector of type 'character'

The issue is that the resulting query, instead of being DT[, sum(b), by=a], becomes DT[, .Primitive("sum")(b), by=a].

The same will happen for any closure:

DT[, f(b), by=a, env=list(f=\(x) sum(x))]
# Error in as.character(jsub[[1L]]) : 
#   cannot coerce type 'closure' to vector of type 'character'

This is not a general issue with [:

DT[, .Primitive("sum")(b), by=a]
#        a    V1
#    <int> <int>
# 1:     1     3
# 2:     2     4
@MichaelChirico MichaelChirico added bug programming parameterizing queries: get, mget, eval, env labels Mar 28, 2024
@MichaelChirico MichaelChirico linked a pull request Mar 28, 2024 that will close this issue
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@MichaelChirico
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Just adding that this is a general issue with [, but it's a bit hard to construct examples AFAICT, which is why it hasn't come up. E.g.

DT = data.table(a = 1:3)
eval(substitute(DT[, foo(a)], list(foo = sum)))
# Error in as.character(jsub[[1L]]) : 
#   cannot coerce type 'builtin' to vector of type 'character'

Directly writing .Primitive("sum")(b) as above is not quite the same -- AIUI it's confusing because .Primitive("sum") is just the deparse() output / print string representation of the LHS.

@jangorecki
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Code without eval call would give better picture what's happening, like verbose via env var

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@jangorecki jangorecki

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bug programming parameterizing queries: get, mget, eval, env
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Use deparse() to cast calls to string when needed Rdatatable/data.table
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@jangorecki @MichaelChirico