expression.project(tape)

An expression that keeps only the selected tape of the original expression.

Preconditions:

• the original expression is multitape.
• the tape number is smaller than the number of tapes.

Postconditions:

• the identities are preserved

Examples

import vcsn
ctx = vcsn.context("lat<lal_char(ab), lan_char(cd), lal_char(ef)>, q")

e = ctx.expression("(a*|<-1>c*|f)(a|\e|f) + (b|c|e)*")
e

$\left(b|c|e\right)^{*} + \left( \left. {a}^{*} \middle| \left\langle -1 \right\rangle \,{c}^{*} \middle| f \right. \right) \, \left(a|\varepsilon|f\right)$

e.project(0)

${b}^{*} + {a}^{*} \, a$

e.project(1)

$\emptyset$

e.project(2)

${e}^{*} + f \, f$