# Why does substitute API in Symbolic.jl returns a tuple instead of a number?

**URL:** <https://discourse.julialang.org/t/why-does-substitute-api-in-symbolic-jl-returns-a-tuple-instead-of-a-number/118582>\
**Category:** General Usage\
**Tags:** symbolics\
**Created:** [August 25, 2024, 2:22am UTC](https://discourse.julialang.org/t/why-does-substitute-api-in-symbolic-jl-returns-a-tuple-instead-of-a-number/118582 "2024-08-25T02:22:57Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![StevenSiew](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevensiew/32/218393_2.png) [@StevenSiew](https://discourse.julialang.org/u/StevenSiew)\
**Post date:** [August 25, 2024, 2:22am UTC](https://discourse.julialang.org/t/why-does-substitute-api-in-symbolic-jl-returns-a-tuple-instead-of-a-number/118582/1 "2024-08-25T02:22:57Z")

</div>

```julia
using Pkg
Pkg.activate("/Users/ssiew/juliascript/Symbolics")
using Symbolics
# using Nemo
# using SymbolicNumericIntegration

@variables x

expr = x 
println("expr is ",expr)

answer = substitute.( expr, (Dict(x => 7),) )
println("answer is ",answer)
print(
"""
Why is the answer "(7,)" instead of just "7"
The documentation for substitute does not explain.
"""
)
#

```

with output:

expr is x  
answer is (7,)  
Why is the answer “(7,)” instead of just “7”  
The documentation for substitute does not explain.

 ![symbolicissue01](https://global.discourse-cdn.com/julialang/original/3X/9/b/9b10dd298820dca79eb57c07ad681f31a89fb176.png)

---

<div class="post-metadata">

**Author:** ![greatpet](https://avatars.discourse-cdn.com/v4/letter/g/e495f1/32.png) [@greatpet](https://discourse.julialang.org/u/greatpet)\
**Post date:** [August 25, 2024, 8:49am UTC](https://discourse.julialang.org/t/why-does-substitute-api-in-symbolic-jl-returns-a-tuple-instead-of-a-number/118582/2 "2024-08-25T08:49:35Z")

</div>

Do you really need broadcast? If not:

```julia
julia> using Symbolics

julia> @variables x
1-element Vector{Num}:
 x

julia> expr = x
x

julia> answer = substitute(expr, Dict(x => 7))
7

```

---

<div class="post-metadata">

**Author:** ![StevenSiew](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevensiew/32/218393_2.png) [@StevenSiew](https://discourse.julialang.org/u/StevenSiew)\
**Post date:** [August 25, 2024, 9:17am UTC](https://discourse.julialang.org/t/why-does-substitute-api-in-symbolic-jl-returns-a-tuple-instead-of-a-number/118582/3 "2024-08-25T09:17:47Z")

</div>

Yes that makes sense

```julia
julia> @variables x y z
3-element Vector{Num}:
 x
 y
 z

julia> expr = x + y + z
x + y + z

julia> answer1 = substitute.( expr, ( Dict(x => 2),Dict(y => 30),Dict(z => 400) )
       )
(2 + y + z, 30 + x + z, 400 + x + y)

julia> answer2 = substitute( expr,Dict(x => 2,y => 30,z => 400) )
432

```