incr(3tcl)

💖 incr — bestie, we're doing MATH 💖

okay so real quick, this page lives in the Tcl Built-In Commands manual, section 3tcl, and it's about the single most iconic lil glow-up a variable can get. it's called incr. it adds. that's it. that's the whole vibe. 💅

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✨ NAME ✨

incr — increment the value of a variable

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🎀 SYNOPSIS 🎀

incr varName ?increment?

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🦋 DESCRIPTION 🦋

so here's the tea: incr increments the value stored in the variable whose name is varName. the value of the variable MUST be an integer — like, non-negotiable, bestie, that's the vibe check. 🫶

if increment is supplied, then its value (which also must be an integer, no exceptions, i'm so serious 😭) gets added to the value of the variable varName. if increment is not supplied, then 1 gets added to varName instead. default behavior = just add one. lowkey the most used line of Tcl in existence ngl.

the new value is stored as a decimal string in the variable varName, and it's also returned as the result. so you get the value AND the side effect. it's giving multitasking. it's giving main character energy. 👑

🌸 starting with the Tcl 8.5 release, the varName passed to incr may be unset — and in that case it will be set to the value of increment, or to the default increment value of 1. glow-up from nothing, we love to see it.

and one more lil situation, bestie: if varName indicates an element that does not exist of an array that has a default value set, then the sum of the default value and the increment (or 1) will be stored in that array element. 💜

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🌈 EXAMPLES 🌈

add one to the contents of the variable x:

incr x

add 42 to the contents of the variable x:

incr x 42

add the contents of the variable y to the contents of the variable x:

incr x $y

add nothing at all to the variable x — and yes, this is genuinely useful, it's often used for checking whether an argument to a procedure is actually integral and generating an error if it is not:

incr x 0

like?? adding zero?? but it checks your types while it does it. not me being obsessed with a no-op. 🙈✨

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👀 SEE ALSO 👀

• expr(3tcl)
• set(3tcl)

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🔥 KEYWORDS 🔥

add, increment, variable, value

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okay bye bestie, go forth and increment responsibly 🧚 this was the incr(3tcl) page from the Tcl crew, and honestly? slay. periodt. 💖🎀🦋