# FinancialToolbox unsupported keyword argument "FlagIsCall"

**URL:** <https://discourse.julialang.org/t/financialtoolbox-unsupported-keyword-argument-flagiscall/94151>\
**Category:** Performance\
**Tags:** package\
**Created:** [February 6, 2023, 4:59pm UTC](https://discourse.julialang.org/t/financialtoolbox-unsupported-keyword-argument-flagiscall/94151 "2023-02-06T16:59:34Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![compleat](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/compleat/32/8958_2.png) [@compleat](https://discourse.julialang.org/u/compleat)\
**Post date:** [February 6, 2023, 4:59pm UTC](https://discourse.julialang.org/t/financialtoolbox-unsupported-keyword-argument-flagiscall/94151/1 "2023-02-06T16:59:35Z")

</div>

Trying to get the FinancialToolbox working as per documentation.

If I try to compute a Put Option value as follows I get an error:

```julia
blsprice(10,10-2.04,.01,1,.1,FlagIsCall=false)

```

results in errors the most relevant here is

```julia
unsupported keyword argument "FlagIsCall"

```

Or perhaps this package is deprecated?

Thanks for any help.

---

<div class="post-metadata">

**Author:** ![nilshg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nilshg/32/2283_2.png) [@nilshg](https://discourse.julialang.org/u/nilshg)\
**Post date:** [February 7, 2023, 9:59am UTC](https://discourse.julialang.org/t/financialtoolbox-unsupported-keyword-argument-flagiscall/94151/2 "2023-02-07T09:59:54Z")

</div>

I don’t think the package is deprecated, given the last updates to it were made on GitHub 3 weeks ago. I think your issue is simply that you have misunderstood the fucntion signature:

```julia
help?> blsprice
search: blsprice

  Black & Scholes Price for European Options

        Price=blsprice(S0,K,r,T,σ,d=0.0,FlagIsCall=true)

```

Here `FlagIsCall` is not a keyword argument, but an optional argument. You can read about the difference between the two here:

[https://docs.julialang.org/en/v1/manual/functions/#Optional-Arguments](https://docs.julialang.org/en/v1/manual/functions/#Optional-Arguments)

(the link takes you to the optional arguments subsection, keyword arguments are discussed in the next section).

tl;dr is this:

```julia
julia> f(x, y = 1) = x + y
f (generic function with 2 methods)

julia> g(x; y = 1) = x + y
g (generic function with 1 method)

```

here `f` has two methods as the optional argument syntax means I’ve created a function which can be called as `f(x)` or `f(x, y)`. `g` on the other hand only has one method, as `y` is a keyword argument, not an optional one.

---

<div class="post-metadata">

**Author:** ![compleat](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/compleat/32/8958_2.png) [@compleat](https://discourse.julialang.org/u/compleat)\
**Post date:** [February 7, 2023, 9:40pm UTC](https://discourse.julialang.org/t/financialtoolbox-unsupported-keyword-argument-flagiscall/94151/3 "2023-02-07T21:40:38Z")

</div>

Oh, OK, thanks. [It would be great if this (about FlagIsCall) could be clarified in the documentation? -For my hundreds of students]